The present invention generally relates to digital signal processing circuits. More particularly, the invention relates to a digital signal processing circuit employed in a magnetic recording and playback apparatus for recording and playing back digital audio signals.
A digital audio tape recorder comprises one type of magnetic recording and playback apparatus having a rotary drum arrangement to record and playback digital audio signals. The digital audio tape recorder is capable of converting an audio signal comprising analog elements into a digital signal for recording and playback. This feature makes it possible to effectively avoid degradation in sound quality while the audio signal is being recorded and playback with high degrees of density.
One way to improve the ease of use and recording quality of the digital audio tape recorder is to switch its recording and playback speeds. This switching, as with conventional analog signal tape recorders, allows magnetic tapes to run at multiples of the standard speed so that the tapes may be run, for example two times, three times, or four times as fast as the standard speed.
Switching the recording and playback speeds of the digital audio tape recorder affords another benefit: widening of the scope of its use. For example, the digital audio tape recorder can also function as an external memory device for use with a computing apparatus. In operation, the recorder records and plays back serial digital data in place of digital audio signals at a speed compatible with the data transmission rate of the computer apparatus.
However, prior art digital audio tape recorders of this kind inevitably lose some digital data in their digital signal processing circuit if the magnetic tape running speeds are simply switched in the same manner as they are on conventional tape recorders. In such digital audio tape recorders, it has been practically impossible to overcome the problems resulting from switching of the recording and playback speeds.